Ahmed El-Baz - Academia.edu (original) (raw)

Papers by Ahmed El-Baz

International Journal of Automotive and Mechanical Engineering, 2021

The present work investigates the dynamic effect of wheel rotation on the aerodynamic characteris... more The present work investigates the dynamic effect of wheel rotation on the aerodynamic characteristics of slick type (ST) wheel of Formula One racing cars using a computational approach. The ST wheel model was compared to experimental results as a validation case. The pressure coefficient over the ST wheel circumference at its middle plane (xy) has been considered as an experimental case from literature and the computed results showed a reasonable agreement. Furthermore, a quantitative evaluation of the numerically-determined wheel drag, local separation and stagnation angles has been also compared to those extracted experimentally from literature. The validation work served by assessing the suitability of using Moving Reference Frame (MRF) method to simulate the effect of wheel rotation, as well as defining the most reliable conditions of testing such as the optimal meshing criteria, the computational domain size, and the adopted turbulence model. According to wheel studies, all com...

ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik

Journal of Wind Engineering and Industrial Aerodynamics, 2022

International Journal of Advance Research, Ideas and Innovations in Technology, 2020

Flow separation is one of the major problems affecting the performance of all airfoils under a hi... more Flow separation is one of the major problems affecting the performance of all airfoils under a high angle of attack. Several passive flow mechanisms have been investigated to limit this phenomenon and improve the aerodynamic efficiency of the airfoil by increasing the lift force while decreasing the drag force associated with it. This study investigates the application of surface bumps over both the suction and pressure sides of the NACA-0018 airfoil at low Reynolds number of 500,000. The bump shapes resemble the shape of the Hawk which does not show a smooth profile in nature. The bumps are introduced in the form of sine waves with different amplitudes and periods. Bumps on each side have been investigated separately, the optimum amplitude and period are determined, the two optimum parameters were joined together forming a new airfoil shape. It was found that this approach limits separation at the stall angle and reduces the drag force as a result of the bumps on the suction side. ...

Journal of Wind Engineering and Industrial Aerodynamics, 2021

Abstract Computational Fluid Dynamics (CFD) has recently provided the needed improvements in simu... more Abstract Computational Fluid Dynamics (CFD) has recently provided the needed improvements in simulation capabilities that allowed enhancing the design of Darrieus wind turbines. While the performance in operating conditions has increased, poor self-starting is still one of the major drawbacks of these machines. In this study, the aerodynamics of Darrieus-turbines during start-up were investigated using a two-dimensional CFD approach. A fluid-structure interaction simulation was carried out using the ANSYS® FLUENT® solver incorporating the sliding mesh technique and enabling the rotational degree of freedom of the Six Degrees of Freedom (6DOF) solver. The issue of translating a fully-resolved flow field into lumped parameters of use to characterize the instantaneous kinematic properties of the airfoils is tackled by means of two velocity sampling methods recently proposed in the literature, i.e. the 2-PointsAverage and LineAverage methods. The results provide a clear estimation of how much the blade local absolute velocity (V∞, L) is dependent on the instantaneous tip speed ratio during the first revolutions of the starting rotor. At λ 1.5, V∞, L decreases significantly during the azimuth positions of 210°

Combustion Science and Technology, 2019

Concentric fuel-rich and fuel-lean mixtures of methane and air were fed in the form of multiple p... more Concentric fuel-rich and fuel-lean mixtures of methane and air were fed in the form of multiple pairs of circumferentially oriented opposing jets that are normal to an air cross flow inside a cylindrical burner to achieve the maximum firing capacity. As two premixed flames developed per each set of concentric jets (while the excess fuel and air diffused into a non-premixed flame wing), combustion via triple flames was thus sustained by a duplicated stagnation impact and a vortical flow field with intense heat recirculation. Setting equivalence ratios of 1.35 and 0.80 for six pairs of opposing jets increased the firing intensity to 100.4 MW/m 3 which corresponded to jet flow velocities of 74.5 m/s. While the maximum blow-out velocity corresponded to a combined equivalence ratio of one, the minimum flame length and the peak combustion efficiency were reached at a combined equivalence ratio of 0.6. Switching from normal to inverse triple flames increased the blowout velocity limit from 74.5 to 82.2 m/s but increased the maximum value of the visible flame length/burner diameter ratio from 1.52 to 1.64.

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2017

The combustion performance of a cylindrical burner accommodating up to six multiple pairs of oppo... more The combustion performance of a cylindrical burner accommodating up to six multiple pairs of opposing methane–air mixtures with a cross-flow of hydrogen was addressed. The cross-flow initially duplicated the stagnation impact and enriched the vortical structures. Aided by the resulting flow strain, the transport of heat and active species from the hydrogen oxidation zone to the methane reaction zones accelerated the combustion across the opposing premixed flames and reduced the peak temperature across the outer diffusion flame. Increasing the cross-flow/opposing jets’ velocity ratio to 0.89 merged the two stagnation centers and maximized the shearing stress. By the slight increase in the velocity ratio to 1.07, the H and OH pools provided for methane combustion became closer to the ports such that a hydrogen/methane mass percent of 10.3% extended the stoichiometric blowout velocity from 28.3 to 35.7 m/s. Since the turbulent kinetic energy thus increased to 8.4 m2/s2, the firing inte...

Volume 4: Fluid-Structure Interaction, 2014

In the present paper, a numerical fluid flow and induced stresses are studied for single hole and... more In the present paper, a numerical fluid flow and induced stresses are studied for single hole and multi-hole orifice plates. Three multi hole configurations are studied; orifice with 3 holes, 5 holes and 7 holes. Turbulence characteristics behind each configuration are analyzed and orifice geometry strength and safety factor are assessed. The multi-hole orifice showed promising results in reducing the turbulence which would increase the system reliability and performance. On the other hand, multi-hole orifice showed weaker strength for same orifice plate thickness and higher probability for pipe wall erosion.Copyright © 2014 by ASME

The present study presents the computational modeling of transitional flow over NACA-0018 airfoil... more The present study presents the computational modeling of transitional flow over NACA-0018 airfoil at low chord Reynolds number of 10 at various angles of attack ranging from 0 to 15 using two-dimensional Reynolds-averaged Navier-Stokes equations (RANS) combined with the Menter’s (γ − ?̃?eθ) transition model. Two different computational domain configurations were optimized in order to investigate the effect of the wind tunnel walls on the developed flow. The structured mesh technique was used for the both domains in order to generate high quality grids that obtain the turbulence model requirements. The numerically predicted results of the airfoil aerodynamic forces presented in terms of lift and drag coefficients as well as boundary layer predictions including surface pressure distribution, skin friction coefficient, mean velocity profiles, RMS velocity profiles and the boundary layer displacement thickness were compared to the experimental data. Very good agreement was attained prio...

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy, 2018

The wake effect is the biggest challenge when locating downwind turbines in wind farms which impo... more The wake effect is the biggest challenge when locating downwind turbines in wind farms which imposes large separation distances between turbines. In the present work, CFD simulations are presented to study possible configurations of wind farms of Savonius wind turbines. The farm is composed by in steps, starting from two-turbine configuration, adding one turbine until reaching a cluster of closely set ten rotors with an average power coefficient of 0.225. This value is very close to the single rotor’s power coefficient. The power density of the cluster is 7.55 W/m2 which is much higher than similar ten turbines located far apart to avoid wake effect. The maximum Cp of a downstream rotor in the cluster reached 0.323 which is about 40% higher than the single rotor. The adopted philosophy for placing downstream rotors is locating the rotor’s returning bucket in the low velocity region of the wake of the upstream rotor to get the least negative torque while the advancing bucket is locat...

Proceedings of the 7th International Conference on Software and Information Engineering - ICSIE '18

In this paper, an architecture is proposed to deliver portable remote online experimentation serv... more In this paper, an architecture is proposed to deliver portable remote online experimentation services. This can benefit the educational and academic sectors in terms of providing remote online accessibility to real experiment setups. Thus, the users can be relieved from geographical and time dependence for the experiment to be conducted. Nowadays, almost all web services leverage the efficiency and prevalence of the REST (Representational State Transfer) architecture. Hence, this proposed remote online service has been implemented in compliance with the RESTful architectural style. Web-based experiments require compatibility with any of the users' portable devices and accessibility at any time. A RESTful architecture can fulfill these requirements. In addition, different experiments can be made available online based on this architecture while sharing the same infrastructure. A case study has been selected to obtain measurements of different force components existing inside wind tunnels. The complete implementation of this system is provided starting from the embedded controller retrieving sensor measurements to the web server development and user interface design.

Due to growing needs for energy in our life, research in the wind energy field has increased sign... more Due to growing needs for energy in our life, research in the wind energy field has increased significantly. There has been global concern towards the development of smart techniques and devices that could optimize the energy conversion and maximize the output power from the wind. Investigating such alternative solutions are required in order to meet the continuous increase in the power demand. The Dual Rotor Wind Turbine system (DRWT) offers higher energy extraction rates from the wind. In the present study, it is proposed to utilize the dual rotor configuration in a ducted system using wind lens in order to enable its application in regions of low wind speeds. The aerodynamic performance of ducted dual rotor wind turbine is investigated using CFD to solve three dimensional, turbulent-steady incompressible flow equations, using the k-ε Realizable and k-ω shear stress transport (SST) turbulence models. Several difficulties due to complexity of geometry and meshing requirements have b...

In Earth to Air Heat Exchanger (EAHE), limited convective heat transfer coefficient and limitatio... more In Earth to Air Heat Exchanger (EAHE), limited convective heat transfer coefficient and limitation of available space have been the main concern of scientists. Thus, reducing the airside thermal resistance using V-shaped porous insert attached to the air path can greatly improve the overall thermal performance and reduce the space needed to achieve the heat transfer process. Thermal performance of the EAHE is usually characterized by the outlet bulk temperature which represents how effective heat can be transferred to the air-side. The pumping power required to overcome the pressure loss across the EAHE however is a dominating factor and must be considered. Using V-shaped porous insert made of highly conductive material, like carbon, copper or aluminum, can efficiently increase the contact area with air and thus decrease the air-side thermal resistance with a reasonable pressure drop. If porous media is inserted normal to the air stream in a closed duct, that would dramatically incr...

In recent years, mobile technology has been rapidly developed and now plays an important role in ... more In recent years, mobile technology has been rapidly developed and now plays an important role in education. Traditional course offerings are on the change towards M-Learning. However, such shift requires combined and integrated efforts from course planners, system designers, software developers, teachers, and students. This paper introduces the design of an online M-Learning interactive teaching and learning platform that has been developed and deployed at the British University in Egypt (BUE). Different real cases of interactive learning applications have been designed, developed, integrated within the platform and evaluated by students. Feedbacks from students show promising results on different aspects; 1) significant improvement of engagement in the learning processes, 2) better understanding of abstract concepts through the visualization interactivity provided through the learning applications. In addition, students showed motivation to use this kind of ICT-based learning techn...

2019 IEEE Conference on Power Electronics and Renewable Energy (CPERE), 2019

This paper presents the design, development and implementation of a remotely accessible wind-tunn... more This paper presents the design, development and implementation of a remotely accessible wind-tunnel testing platform. NI CompactDAQ has been selected to act as the primary control unit, which is connected to the host PC with the developed web-application to enable the remote accessibility. The web-application has been developed based on LabVIEW to ensure smooth compatibility with the NI device. The web-application includes multiple-interfaces corresponding to different measurement scenarios. This includes; 1) variable speed operation of the wind-tunnel fan, 2) three force balance to measure drag, lift and moment forces on a test airfoil within the tunnel test section, 3) torque and rpm of an external rotor. Testing has been performed both on-site and remotely, where no measurement delay has been observed in the online testing. The implemented testing platform serves for both undergraduate students as well as postgraduates in relevant courses related to wind-energy.

Julius-Kühn-Archiv, 2018

Chemical control especially fumigants is the most commonly used method to control stored-grain pe... more Chemical control especially fumigants is the most commonly used method to control stored-grain pests. A safer alternative for disinfestation is by heating up grains to a temperature of 50-60 °C. However, this alternative consumes high thermal energy due to the relatively high temperature required to achieve the required goal. Using solar energy as heat source for low temperature applications has become a viable mean for heating applications. Heating of grains using solar energy requires special design of grain storage system as well as development of efficient heat transfer mechanism to increase grain temperature over a limited period of time. The main objective of the current study is to use thermal disinfestation as a non-chemical, safe control method for grain management. A heating system based on solar energy has been developed as heat generator to control stored-grain insects. The target temperature range is 50-60 °C, which is enough to kill most of stored-grain insects. The gr...